. ♪ >> reporter: dancer rachel lincoln says her job it -- her job is to make this look easy which it is not. >> you made it to be really strong honestly to do this work. gravity is there all the time. we're not gravity defying. so your poor muscles and all the strength in your back and stomach have to hold your body up to create the illusion that you're standing on a wall. >> reporter: the only way to understand just how hard this is is to try it. >> i want you to just realize where you are. >> reporter: amelia took me to the great wall of oakland, california, the troupe's home base. >> reporter: that is locked. they put me in a safety harness -- >> the word danger -- >> reporter: i love that it says "danger" right on here. and before i knew it -- here we go over the wall. >> two of us together. hanging out on the wall in oakland. >> reporter: we were 115 feet in the air, and i learned how tough this really is. >> your core has to be really strong. your general fitness level has to be high. give me your hand. run. good. >> reporter: that is the most fun. >> back -- turn your head to